1. Field of the Invention
The present invention relates to a connection structure for power supply to a vehicle door which supplies an electric power of a vehicle body to auxiliary members in a back door, etc. of an automobile.
2. Description of the Related Art
Generally, various auxiliary members such as a rear wiper motor, a defogger, a door lock, etc. are mounted on a back door of an automobile, and there have been proposed a number of connection structures for power supply to a vehicle door.
FIG. 14 shows a conventional connection structure for power supply to the vehicle door as described in Japanese Utiltiy Model Publication No. 57-47444 of an unexamined application. As seen in FIG. 14, a plurality of pin-like movable terminals 121 are provided on a back door 120 of a vehicle so as to be retractable by means of coil springs 122, and contact terminals 124 are provided on a vehicle body 123 so as to face with tip ends 121a of the movable terminals 121 respectively.
Each of the movable terminals 121 is exposed only at its tip end 121a, and all the other area is covered with an insulating holder 125. One (124.sub.1) of the contact terminals 124 has a cancel switch mechanism 127 which is biased by a coil spring 126 so as not to contact with a contact 128 when the door is open. The contact terminals 124 are pressed into contact with the movable terminal 121 when the door is closed, and the contact terminal 124.sub.1 comes in contact with the contact 128 thereby to connect a power source side circuit 130 to a circuit (not shown) of the auxiliary devices.
However, the back door 120, which communicates with a trunk space must be frequently opened and closed, and there has been a problem in the above described structure that, due to the exposed contact faces of the terminals 121 and 124, baggage may interfere with the contact faces, or sand, dust water drops, or other foreign articles, may enter between the contact faces of the terminals, thus resulting in a faulty electrical connection. In other words, due to the structure wherein the 15 terminals 121, 124 face with each other to contact, dust, or the like, can accumulate between the contact faces because they are not cleaned when an erosion has occurred or the foreign articles are adhered to the contact faces, and therefore, a defective contact may occur. Because the contact terminal 124, particularly at the vehicle side, is exposed and always supplied with an electric voltage, it has been necessary to provide an electric power shut off mechanism (for example, a cancel switch mechanism) in order to avoid a short circuit which will be caused by a contact with a conductive foreign article. This has inevitably made the structure complicated. Further, the movable terminal 121 is liable to be displaced radially and inclined on occasion of contacting, due to its long size. Therefore, the contact area of the contact terminal 124 must be large in order to obtain a reliable contact even in such cases. In addition, when a contact 129 is inclined and displaced, there has been a fear that contactability of the cancel switch mechanism 127 may deteriorate and cause a faulty contact. Still further, in order to deal with an overstroke when the back door 120 is closed with a strong force, the movable terminal 121 must have an ample space for the stroke, which results in an increase in the size of the structure.